FAST RADIO BURST/GAMMA-RAY BURST COSMOGRAPHY

Abstract

Recently, both theoretical arguments and observational evidence suggested\nthat a small fraction of fast radio bursts (FRBs) could be associated with\ngamma-ray bursts (GRBs). If such FRB/GRB association systems are commonly\ndetected in the future, the combination of dispersion measure (DM) derived from\nFRBs and redshifts derived from GRBs makes these systems a plausible tool to\nconduct cosmography. We quantify uncertainties in deriving the\nredshift-dependent DM_{IGM} as a function of z, and test how well dark energy\nmodels can be constrained with Monte Carlo simulations. We show that with\npotentially several 10s of FRB/GRB systems detected in a decade or so, one may\nreach reasonable constraints on wCDM models. When combined with SN Ia data,\nunprecedented constraints on dark energy equation of state may be achieved,\nthanks to the prospects of detecting FRB/GRB systems at relatively high\nredshifts. The ratio between the mean value < DM_{IGM} (z)> and luminosity\ndistance (D_{L} (z)) is insensitive to dark energy models. This gives the\nprospects of applying SN Ia data to calibrate < DM_{IGM} (z)> using a\nrelatively small sample of FRB/GRB systems, allowing a reliable constraint on\nthe baryon inhomogeneity distribution as a function of redshift. The\nmethodology developed in this paper can also be applied, if the FRB redshifts\ncan be measured by other means. Some caveats of putting this method into\npractice are also discussed.\n